1. Field of the Invention
The present invention relates to a method and an apparatus for enabling duplication preventing control depending on an extracted additional information which may be done by outputting an image signal superimposing an additional information and then receiving such image signal to extract the superimposed additional information and also relates to an image signal recording medium, for example, in such a case that an image signal recorded in a recording medium is reproduced, it is then transmitted together with a duplication preventing signal and the transmitted image signal is received to limit or inhibit recording thereof to the other recording medium.
2. Description of the Related Art
A VTR (Video Tape Recorder) is widely used and many software applications which may be reproduced by the VTR are now available. Particularly, a regenerating apparatus such as a digital VTR and DVD (Digital Video Disk) is appearing as novel apparatus in these days. Therefore it is now possible to enjoy the image and sound of high quality and high fidelity by easily regenerating the recorded image and sound.
However, in one hand, such excellent apparatus has brought about a new problem that abundant software applications which are available in the market are probably copied without limitation and various kinds of duplication preventing measures have been considered.
For example, although it is not a method to prevent directly the duplication of analog image signal, a method for substantially preventing the duplication has been proposed. In this method, difference in the AGC (Auto Gain Control) systems between the VTR as the recording apparatus and a monitor receiver for providing images is used or difference in the APC (Auto Phase Control) thereof is used for the purpose of preventing duplication of software applications.
Namely, the former method utilizes difference of the AGC system in which VTR, for example, performs AGC using a pseudo synchronous signal inserted in the image signal, while the monitor receiver employs the AGC system not depending on such pseudo synchronous signal. In this case, at the time of recording an analog image signal into an original recording medium, a pseudo synchronous signal of extremely higher level is superimposed as the synchronous signal for AGC to such analog signal and thereby the pseudo synchronous signal of extremely higher level is inserted to the synchronous signal for AGC into the image signal to be supplied to the recording VTR from the regenerating VTR.
Moreover, in the latter method, difference of such APC characteristic that APC follows a color burst signal with a short time constant in the VTR but it follows with a comparatively longer time constant in the monitor receiver. Namely, at the time of recording an analog image signal into an original recording medium, phase of a color burst signal of the image signal is partially inverted and thereby the signal in which the phase of the color burst signal is partially inverted is output as the image signal supplied to the recording VTR from the regenerating VTR.
In the case explained above, in the monitor receiver which receives supply of an analog image signal from the regenerating VTR, image signal is normally reproduced without receiving any influence of the pseudo synchronous signal and partial phase inversion of the color burst signal used for APC.
However, in the VTR which records the signal to a recording medium by receiving the analog image signal which has superimposed the pseudo synchronous signal as explained from the regenerating VTR or is subjected to the phase inversion control of the color burst signal, it is impossible to normally realize the gain control or phase control depending on the input signal and thereby the image signal cannot be recorded normally. Accordingly, if the recorded image signal is reproduced, the normal image to enjoy excellent image and sound can no longer be reproduced.
In the case of processing the analog image signal, duplication is not inhibited but it is made impossible to obtain the reproduced signal which cannot used for watching and hearing and this method is rather concluded as the so-called negative duplication preventing control.
On the other hand, in the case of the processing the digital information, for example, the digital image signal, a direct duplication preventing control is executed to inhibit the duplication by adding a duplication preventing control signal consisting of a duplication preventing code or a duplication generation limiting code to the image signal as a digital data and thereby recording such code and image signal to a recording medium.
FIG. 1 shows a basic structure of a duplication apparatus for processing a digital information. In this structure, a digital information reproduced by a digital regenerating apparatus 110 is sent to a digital recording apparatus 120 via a digital transmission line 101 and thereby such digital information which is allowed to be duplicated is duplicated but the information which is not allowed is inhibited for duplication.
In a recording medium 111 loaded in the digital regenerating apparatus 110, a duplication preventing control information as an additional information is recorded in addition to a digital main information. This duplication preventing control information instructs duplication inhibit, duplication acknowledgment, limitation of duplication generation as the details of control. A digital regenerating means 112 reads information from the recording medium 111 to obtain the duplication preventing control information with the digital main information and then sends such pieces of information to a digital recording apparatus 120 via a digital transmission line 101.
A duplication preventing control signal detecting means 122 of the digital recording apparatus 120 detects the duplication preventing control signal from the information received via the digital transmission line 101 to discriminate details of control and then transfers this discrimination result to the digital recording means 121.
The digital recording means 121 converts, when discrimination result of the duplication preventing control signal from a duplication preventing control signal detecting means 122 allows recording of the digital information input from the digital transmission line 101, the input digital signal into the digital information suitable for recording and executes the recording by writing such digital information into the recording medium 123. On the other hand, when the discrimination result of the duplication preventing control signal from the duplication preventing control signal detecting means 122 does not allow duplication, the digital recording means 121 does not execute the recording of the input digital information.
Moreover, when the discrimination result of the duplication preventing control signal from the duplication preventing control signal detecting means 122 allows only first duplication generation, the digital recording means 121 converts the input digital to the digital information suitable for recording and executes the recording by writing such digital information to the recording medium 123 and also changes the duplication preventing control signal as the additional information into the signal to instruct inhibit of duplication (inhibit of duplication of the next generation) and also records such inhibit signal to the recording medium 123. Therefore, it is impossible to duplicate the image signal using the duplicated recording medium 123.
As explained above, in the case of the so-called digital connection in which the main information signal and the duplication preventing control signal as an additional information are supplied to the recording apparatus as the digital signals, a duplication preventing control signal is included in the digital data to be transmitted. Therefore, the recording apparatus surely can execute the duplication preventing control such as inhibit of duplication by utilizing such duplication preventing control signal.
Meanwhile, when the digital VTR of FIG. 1 is for example a digital VTR, in view of monitoring the reproduced image signal and voice signal, only the image signal as the main information signal and the voice signal are converted to analog signals via a D/A converting circuit 113 and these analog signals are usually led to an analog output terminal 114 to which a monitor receiver is connected.
As explained, even in the case of the digital information regenerating apparatus, the duplication preventing control signal is not included in the analog signal connected to the analog output terminal 114. Therefore, using the analog connection for connecting an analog VTR to the analog output terminal 114, duplication of information signal is possible.
Therefore, it is considered to add, by superimposition, the duplication preventing control signal to the D/A converted image signal and voice signal, but it is difficult to add the duplication preventing control signal and then extract it in the recording apparatus to use for duplication preventing control without any deterioration of the D/A converted image signal and voice signal.
Therefore, for the analog connection, it has been only way, as the negative duplication preventing method, to introduce the duplication preventing method utilizing difference of AGC systems between the VTR and monitor receiver or difference of APC systems thereof.
However, in the case of the duplication preventing control method utilizing difference of AGC systems or APC systems between the VTR and monitor receiver as explained above, the image signal can be recorded normally depending on the AGC system or APC system in the recording apparatus side, yet disabling the negative duplication preventing method. Moreover, it has also been possible that reproduced image on the monitor receiver is disturbed.
As a duplication preventing control system which has solved the problems explained above and is effective for any of the analog connection and digital connection without deterioration of image and voice to be reproduced, the applicant of the present invention has proposed a system in which the image signal is recorded in digital or analog by spreading the spectrum of the duplication preventing control signal and then superimposing the spread spectrum duplication preventing control signal on the image signal of the analog signal condition (Japanese Patent Application No. HEI 7-339959).
In this system, the pseudo random noise code (hereinafter referred to as the PN code) used as the spreading code is generated at a sufficiently higher velocity and this code is then multiplied to the duplication preventing control signal for the purpose of spectrum spreading and thereby to convert the narrow band and high level duplication preventing control signal into the broad band and low level signal which does not give any effect on the image signal and voice signal. This spread spectrum duplication preventing control signal is superimposed on the analog image signal and then is recorded on a recording medium. In this case, the image signal recorded on the recording medium may be analog signal or digital signal.
In this system, since the duplication preventing control signal subjected to spectrum spread is then superimposed on the image signal as the broad band and low level signal, it is difficult for a person who is trying to make illegal duplication to extract the superimposed duplication preventing control signal from the image signal.
But, it is possible to detect the duplication preventing control signal superimposed by executing inverse spectrum spread and use it for a certain purpose. Therefore, the duplication preventing control signal can surely be provided in combination with the image signal to the recording apparatus side and the duplication preventing control signal can also surely be detected in the recording apparatus side to reliably execute the duplication control depending on the duplication preventing control signal.
But, as explained above, in the case of the system where the spread spectrum duplication preventing control signal is superimposed on the image signal, the spread spectrum duplication preventing control signal is sometimes eliminated, deteriorated or changed.
For example, a noise reduction system for reducing noise of the image signal by utilizing the correlation between pixels in the horizontal direction of the image signal (hereinafter referred to as correlation in the horizontal direction), correlation between horizontal scanning lines (hereinafter referred to as correlation in the vertical direction), correlation between fields or correlation between frames takes a difference of image signals between the pixels in the adjacent horizontal direction or between the horizontal scanning lines and eliminates the difference obtained as noise.
When such noise reduction system is used, the spread spectrum duplication preventing control signal superimposed on the image signal is detected as a difference and it is probably eliminated as explained above. Moreover, when such duplication preventing control signal is eliminated, it is also probable that the other spread spectrum duplication preventing control signal is newly added.
In addition, when the noise reduction system utilizing the correlation of the horizontal direction or correlation in the vertical direction of the image signal is used, the duplication preventing control signal may sometimes be deteriorated, for example, the duplication preventing control signal superimposed on the image signal is partly eliminated, although not all of the spread spectrum duplication preventing control signal superimposed on the image signal. In such a case, the accurate duplication preventing control signal superimposed on the image signal cannot be extracted, disabling duplication preventing control depending on the duplication preventing control signal.
Furthermore, in the case of enlarging or compressing an image reproduced by the image signal on which the spread spectrum duplication preventing control signal is superimposed by utilizing a so-called zoom mode, the image signal is interpolated by the other adjacent image signal or the image signal is curtailed. In this case, since the spread spectrum duplication preventing control signal superimposed on the image signal changes, if the inverse spread spectrum is performed, the original duplication preventing control signal before the spread spectrum cannot be extracted normally in some cases.
Moreover, when the so-called wide mode in which the image of vertical and horizontal ratio of 9:16 is formed using the image signal to form an image in the vertical and horizontal ratio of 3:4 or the so-called cinema mode in which the vertical direction of image is compressed to form an image in the same vertical and horizontal ratio as the movie screen are used, since the interpolation and curtailment are performed for the image signal, the original spread spectrum duplication preventing control signal superimposed on the image signal may be deteriorated. Even when the image display size conversion is performed as explained above, it is possible in some cases that that the spread spectrum duplication preventing control signal superimposed on the image signal cannot be extracted as the original normal duplication preventing control signal.
In addition, even when only the necessary part of the image of one image frame formed by the image signal is used or the unnecessary image part, on the contrary, is deleted, the spread spectrum duplication preventing control signal superimposed on the image signal may be changed. As explained above, even when a part of the image formed by the image signal is used or deleted, the original duplication preventing control signal cannot be extracted.
Moreover, when reproduction is performed in various speeds in the VTR like the specified lower speed reproduction or higher speed reproduction, the image signal of one field may be missed or doubled. Therefore, in the recombined image signal, the spread spectrum duplication preventing control signal is no longer continuous and thereby the inverse spread spectrum will probably disable the recovery of the duplication preventing control signal.
Moreover, when the cutting edition is performed to curtail the image signal in unit of the field, the spread spectrum duplication preventing control signal is no longer continuous in the image signal after the cutting edition and inverse spread spectrum will also probably disable the recovery of the duplication preventing control signal.
Moreover, when the image signal of NTSC system is converted to the PAL system image signal and the image signal of the PAL system is converted, conversely, to the NTSC image signal as the image signal conversion, since the number of the horizontal scanning lines forming a frame is different depending on each system, the interpolation is performed by curtailing the image signal of the adjacent horizontal scanning line or the horizontal scanning lines and thereby the accurate duplication preventing control signal superimposed on the image signal cannot be extracted, disabling the duplication preventing control depending on the duplication preventing control signal.
For example, the image signal of the NTSC system forms an image of one frame with 525 horizontal scanning lines, while the image signal of the
system forms an image of one frame with 625 horizontal scanning lines. In the case of converting the image signal of NTSC system into the image signal of PAL system, the interpolation of horizontal scanning line is performed and in the case of converting the image signal of PAL system into the image signal of NTSC system, the horizontal scanning lines are curtailed.
As explained, when the spread spectrum duplication preventing control signal is deteriorated because the image formed by the image signal to which the spread spectrum duplication preventing control signal is superimposed is enlarged or compressed, or system conversion of the image signal is performed or reproduction is executed in the various speeds or cutting edition is performed, since the original duplication preventing control signal cannot be extracted, the duplication preventing control depending on the duplication preventing control signal cannot be executed.